XY_LOOP_MODE: replace old points with new ones, using the maximum size
of the view
XY_FORCE_MODE: append_forced sets those and only those points
and we crash if we pass too much points
this is like timeview but the plotting is done at frame/subframe
resolution of a given reference clock signal, let's say.
The realtime information of the events is not used. It's all
logical.
It will be used to log harq processes for the moment.
Cedric Roux